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SummaryThe human retrovirus HTLV-1 causes a hematological malignancy or neuroinflammatory disease in ∼10% of infected individuals. HTLV-1 primarily infects CD4+ T lymphocytes and persists as a provirus integrated in their genome. HTLV-1 appears transcriptionally latent in freshly isolated cells; however, the chronically active anti-HTLV-1 cytotoxic T cell response observed in infected individuals indicates frequent proviral expression in vivo. The kinetics and regulation of HTLV-1 proviral expression in vivo are poorly understood. By using hypoxia, small-molecule hypoxia mimics, and inhibitors of specific metabolic pathways, we show that physiologically relevant levels of hypoxia, as routinely encountered by circulating T cells in the lymphoid organs and bone marrow, significantly enhance HTLV-1 reactivation from latency. Furthermore, culturing naturally infected CD4+ T cells in glucose-free medium or chemical inhibition of glycolysis or the mitochondrial electron transport chain strongly suppresses HTLV-1 plus-strand transcription. We conclude that glucose metabolism and oxygen tension regulate HTLV-1 proviral latency and reactivation in vivo.

The "Applied Simulations and Integrated Modelling for the Understanding of Harmful Algal Blooms" (Asimuth) project sought to develop a harmful algal bloom (HAB) alert system for Atlantic Europe. This was approached by combining, at a national or regional level, regulatory monitoring phytoplankton and biotoxin data with satellite remote sensing and other information on current marine conditions, coupled with regional scale models that included a representation of HAB transport. Synthesis of these products was achieved by expert interpretation within HAB risk alert bulletins that were prepared on a regular basis (typically weekly) for use by the aquaculture industry. In this preface to the Asimuth Special Issue we outline the main HAB species of concern in the region and the strengths and limitations of different methodologies to provide early warning of their blooms.

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Forest fires have intensified in the Mediterranean area over the last decades, becoming increasingly destructive. Catastrophic wildfires, such as the ones that occurred on the Portuguese territory during 2017, have emphasized the need for developing management tools capable of rapidly assessing their impact on downstream water bodies. This study focuses on the effects of the 2017 forest fires on the water quality of the Zêzere River (Portugal), one of the major sources of freshwater to Lisbon and the surrounding areas. During 2017, more than 100,000 ha (30% of the Zêzere watershed) were affected by wildfires, making it one of the largest burned areas in Portugal. Using the soil water assessment tool, the land use (curve number, crop vegetation management factor) and soil (soil erodibility factor) parameters were modified considering different magnitudes of the fire event (low, medium, and high severity). The impact of the different wildfires was then assessed at the subbasin level and at the entrance of Castelo de Bode reservoir. Simulations showed a significant increase in runoff and sediment concentration at the subbasin level in the years following the fire events, with high concentrations of nutrients occurring at the reservoir inlet. Nitrate concentration slightly overcame the threshold limits foreseen in legislation for drinking water, meaning that fires could have additional impact on human health. Phosphate concentration recurrently exceeded the legislation threshold, representing a severe risk to the ecosystem by potentially promoting the eutrophication of downstream water bodies, oxygen deficiency in the bottom substrate, and reduced biodiversity.